Mortise locks are typically designed to fit into an opening provided in the edge of a door opposite the edge that is hinged to the door frame. The lock generally includes a latch bolt movable between an extended position (where the latch bolt projects beyond the edge of the door into an opening in the door frame to latch the door closed) and a retracted position (where the latch bolt is in position to permit opening of the door). Mortise locks also typically include a dead bolt that is movable between an extended position (where the dead bolt projects beyond the edge of the door into an opening in the door frame to lock the door) and a retracted position (where the dead bolt permits opening of the door). Mortise locks are typically configured so that the inner door knob can be rotated to retract the latch, and the outer door knob can be rotated to retract the latch.
A door may be hinged to a door frame along its left side edge or its right side edge. A conventional mortise lock mounted in the left edge of a door must be reversed when the lock is mounted in the right side edge of a door so that the inner and outer door knobs of a left-side mounted lock become the outer and inner door knobs, respectively, of a right-side mounted lock. Thus, adjustments must be made to the conventional mortise lock depending on whether it is mounted in a left-side or right-side orientation.
Adjustments to the conventional mortise lock are typically accomplished by partially or totally disassembling the mortise lock and rearranging or configuring the mortise lock components to achieve the desired mode of operation. However, the task of disassembling the mortise lock is a time consuming process. Furthermore, disassembling the mortise lock provides opportunities for damaging the lock components. Additionally, components may become lost during the adjustment process. If replacement components are not available, the mortise lock will have to be replaced.
U.S. Pat. No. 4,695,082 discloses a reversible mortise lock in which its housing need not be opened in order to reverse the door knob operation, so that one knob or the other is optionally prevented from retracting the latch.
Likewise, U.S. Pat. No. 5,678,870 discloses a reversible mortise lock that does not have to be opened and components need not be removed from the mortise lock in order to reverse the door knob operation.
A typical mortise lock uses a cam shaped hub working through several plates and levers to retract the latch bolt against spring tension. There are usually two or more springs used in a mortise lock. One spring serves to keep the latch fully extended. This is typically a relatively soft spring. In addition, there are typically one or more other springs that serve to hold a pair of levers in a horizontal position, or keep a pair of knobs in the correct orientation. Differing degrees of spring tension are required for levers and knobs.
A pair of levers requires a strong spring to support the weight of the levers which are cantilevered from the spindle centerline. The levers also require a strong spring because pressure is applied to the levers at a distance of, e.g., abut 2xc2xd inches from the spindle centerline. In order to provide a comfortable feel for the levers, relatively stronger springs are required.
Knobs require a softer spring because knob diameters rarely exceed 2xc2xc inches. This results in a lever arm of just 1xe2x85x9 inches. This shorter lever arm develops less leverage when retracting the latch bolt. In order to provide for a comfortable feel, relatively soft springs are used. In addition, because the knobs are balanced on both sides of the spindle, there is no weight cantilevered on one side of the spindle and there is no weight to be supported by these springs.
A problem with past mortise locks is that there is a lack of adjustability for the springs in the latch bolt retraction system to provide for use of either or both knobs and levers in the mortise lock such that the mortise lock does not have to be opened and components need not be removed from the mortise lock.
Since a typical mortise lock can be installed in one of two basic orientations (dead bolt up or dead bolt down), the door hubs must rotate in two directions. As indicated above, when levers, rather than a round door knob, are used with a mortise lock, they put pressure on the spring or springs associated with their hub. Springs will, over time, lose some ability to apply a force. This allows the levers to xe2x80x9csagxe2x80x9d. To combat the impression of xe2x80x9csag,xe2x80x9d many lock manufacturers will introduce a small amount of xe2x80x9cpresetxe2x80x9d by slightly rotating the square hole in their latch hubs. But, since a typical mortise lock allows for installation and therefore rotation in two directions, this would require the consumer to disassemble the lock to reverse the hub when installing the lock. Again, this often leads to the customer losing parts and additional difficulties as described above. It would therefore be desirable to provide an apparatus that enables xe2x80x9cpresetxe2x80x9d to be changed without disassembling the lock.
A mortise lock is provided which includes a casing having a front plate for confronting a door frame and a pair of opposed side walls, the front plate having an opening for a latch bolt. A latch bolt is movable with respect to the casing between an extended position and a retracted position by a linkage connected to a hub to receive a door handle shaft, the latch bolt is rotatable axially, and the hub is rotatably secured between the opposed side walls of the casing. A slider plate for initiating movement of the linkage is provided that is movable from a first position wherein the linkage moves the latch bolt to the retracted position to a second position wherein the linkage moves the latch bolt back to the extended position. The slider plate may have a preset adjuster, adjustable through at least one access aperture in the casing. An adjustable spring may be included to urge the slider plate in a direction away from the hub to cause the slider plate to move to the second position and an access aperture is included in the casing to facilitate access to the adjustable spring.
The linkage may include a latch body carrier having a latch bolt spring guide and a latch bolt spring held in place by a latch bolt spring retainer, and a latch actuation lever connected between the slider plate by at least one pivot pin.
The hub may have a main body and a first and a second hub wing extending from the main body. Here, the slider plate has an upper member or block and a lower member or block, the upper member having an adjustable portion thereon to adjust preset in one direction. The adjustable portion is adapted to contact the first hub wing when the hub is rotated in a counterclockwise direction. The lower member has a second adjustable portion thereon to adjust preset in another direction, the second adjustable portion adapted to contact the second hub wing when the hub is rotated in a clockwise direction. Rotation of the hub in either a clockwise or counterclockwise direction causes substantially identical movement of the slider plate to cause the latch bolt to retract and extend. At least one spring is used to urge the slider plate in a direction away from the hub to cause the slider plate to move to the second position. Preferably, the adjustable portions are accessible for adjustment through the casing. The linkage preferably includes a latch body carrier having a latch bolt spring guide and a latch bolt spring held in place by a latch bolt spring retainer, and a latch actuation lever connected between the slider plate by at least one pivot pin.
An adjustable spring may be provided to urge the slider plate in a direction away from the hub to cause the slider plate to move to the second position. An access aperture in the casing is preferably provided to facilitate adjustment of the adjustable spring.
The adjustable spring may include a floating spring adjuster plate having a threaded hole therein, a spring adjusting screw to be received between the threaded hole and the casing and at least one spring between the floating spring adjuster plate and the slider plate. Rotation of the screw within the threaded hole through the access aperture causes the distance between the spring adjuster plate and the front plate of the housing to change. Preferably, the spring is a pair of concentric coil springs where one spring is shorter than the other spring. Alternatively a spring having a nonlinear spring rate may be used.